Ultra hard communications antenna

ABSTRACT

A ground-to-air antenna capable of withstanding all overpressures outside the crater of a nuclear explosion including a massive reinforced concrete block having one exposed surface flush with the surrounding terrain, copperplating the reinforcing members and placing an insulation-filled wave guide in the concrete and connecting it to a sending and receiving means, while the impedance of the wave guide is matched to that of free space.

United States Patent [191 Carrell 1 Nov. 27, 1973 ULTRA HARDCOMMUNICATIONS ANTENNA [75] Inventor: Terry E. Carrell, Los Angeles,Calif.

[73] Assignee: The United States of America as represented by theSecretary of the United States Air Force, Washington, DC.

22 Filed: Mayll, 1966 21 Appl. No.: 550,879

[52] US. Cl 343/719, 343/770, 343/873 [51] Int. Cl. H01q 1/04 [58] Fieldof Search 343/719, 873, 897; 325/15 [56] References Cited I UNITEDSTATES PATENTS 2,980,793 4/1961 Daniel 343/719 X 2,992,325 7/1961Lehan.... 343/719 X 3,216,016 l/1965 Tanner 343/719 3,273,152 9/1966Earp 343/719 X OTHER PUBLICATIONS Pulse, Collins Radio Company EmpoyeeBulletin, Vol. 6, No. 1, January, 1966, page 2.

Primary Examiner-Benjamin A. Borchelt Assistant Examiner-Richard E.Berger Attorney--I-larry A. Herbert, Jr. and Sherman l-I.

Goldman [57] ABSTRACT A ground-to-air antenna capable of withstandingall overpressures outside the crater of a nuclear explosion including amassive reinforced concrete block having one exposed surface flush withthe surrounding terrain, copperplating the reinforcing members andplacing an insulation-filled wave guide in the concrete and connectingit to a sending and receiving means, while the impedance of the waveguide is matched to that of free space.

6 Claims, 5 Drawing Figures PAIENTEDNUVQY 1915 3775.772

INVENTOR. 7156?) 6'. 641F721;-

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ULTRA HARD COMMUNICATIONS ANTENNA The invention relates generally toground-to-air antennas and more particularly to a hard antenna capableof withstanding all overpressures outside the crater of a ground nuclearexplosion.

In the event of a nuclear attack utilizing high-yield nuclear weaponsthe national defense system must be able to communicate in order toinstitute proper defensive measures.

The communication I am chiefly concerned with is communication betweeneither an underground command post and an air-borne command post orattack aircraft.

A conventional aboveground antenna would obviously be destroyed by theeffects of blast and heat caused during a nuclear explosion, therefore,any antenna constructed must be built at ground level or below in'orderthat it may survive such effects.

While the concept of underground antennas is not entirely new thethought of an underground antenna which will withstand an overpressureof 2000 pounds per square inch (psi) and still be able to communicatewith aircraft 200 miles distance is thought to be inventive. With my newstructure, I provide for transmitting omni-directional radiation orunidirectional radiation and still receive in a horizontal plane.

It is therefore an object of this invention to provide a method andapparatus which will provide ground-toair communication during and aftera nuclear explosion.

It is a further object of this invention to provide an antenna whichwill withstand the heat and blast effects of a nuclear explosion.

It is another object of this invention to provide an antenna which iscapable of withstanding an overpressure of 2,000 pounds per square inch.

It is still another object of this invention to provide a ground-to-airantenna which is mounted in a flush ground plane.

It is still a further object of this invention to provide an antennawith no vertical protruding parts which can be broken off by high windsor projectiles.

It is another object of this invention to provide an antenna for ultrahigh frequencies which is mounted in a hard structure capable ofwithstanding the effects of a nuclear explosion.

It is another object of this invention to provide an ultra highfrequency antenna which will not be effected by atomic radiation of anuclear blast.

These and other advantages, features and objects of the invention willbecome more apparent from the following description taken in connectionwith the illustrative embodiments in the accompanying drawings, wherein:

FIG. 1 shows a top view of a hardened omnidirectional antenna structure;

FIG. 2 is a side elevation view in section of a hardenedomni-directional antenna structure;

FIG. 3 is a side elevation view in section of a hardened unidirectionalantenna structure embodied in this invention;

FIG. 4 is a cross sectional view of a hardened unidirectional antennastructure included in this invention; and

FIG. 5 is a cross sectional view of the T-feed utilized to excite theslots of the antennas.

Fundamentally, the antenna of my invention consists of a flush mountedslot array in which the slots have been filled with an insulatingmedium. The complete absence of any structure above the ground levelgives the design a freedom from drag loading which other antennas cannotclaim. Under most circumstances the thermal and reflected overpressureeffects will be less serious than for conventional designs. At the sametime, it is not forced to operate at the extremely low efficiencies ofthe ordinary buried antennas.

As is known in the art the slot dipole antenna is essentially thecomplement of the conventional dipole antenna. That is, a conventionaldipole consists of a conductor of a prescribed size surrounded by aninsulator (usually air) while a slot dipole consists of an insulator ofthe prescribed size surrounded by a conductor (usually copper). If aconventional dipole is held horizontally with respect to the earthssurface, the radiation from it is horizontally polarized. On the otherhand, if a slot dipole is held horizontally with respect to the earthssurface its radiation is vertically polarized. Both, however, areefficient radiators if properly designed.

Referring now to FIG. 1 there is shown a plan view of my antenna whichis a substantial omni-directional array. The circular concrete slab 10has embedded therein welded wire fabric 12 which may be of the typecommonly utilized in reinforced concrete. At least the top three layersof the wire screen 12 are copperplated. The skin effect will causealmost all of the radio frequency power to flow through the copperplatedlayer, hence the conductivity will be the same as if the entire screenwere made of copper. Further, if the mesh spacing in this screen issmaller than about a quarter wavelength at the highest frequency to beused, the reinforcing fabric will appear to the radio frequency energyas essentially a solid sheet of copper, giving the antenna body a highelectrical efficiency. The antenna feed is shown by the crossed slot 14.

The side elevation view in section, of the antenna is shown in FIG. 2,the concrete slab 10 with the copperplated wire 12 and the antenna feedat 14. In this illustration only three layers of wire mesh are shown butit is anticipated that mechanical requirements for hardness will requiremore layers which could be utilized as part of this antenna.

The array shown in FIGS. 1 and 2 is designed for use with a transmitterat a deep underground site. By putting the transmitter in thecommunications center of the subterranean command post rather than atthe antenna, the shock mounting problem is largely avoided and rapidservicing is possible in the event of transmitter or receiver failure.

An item of major concern arises with this arrangement however, and thatis the excessive amounts of power wasted because of the inefficienciesin transmission lines. Such a problem is overcome by mounting the radiofrequency circuitry of the receiver and transmitter within the antennaas shown in FIGS. 3 and 4. The same solution may be used for theomni-directional antenna by adding an instrument silo 18 to theconfiguration shown in FIGS. 1 and 2. The large, heavy, andheat-generating power supply and delicate modulator will still be leftat the command center to minimize shock mounting problems.

The antenna array of FIGS. 3 and 4 is substantially the same as thatdescribed with regard to FIGS. 1 and 2, the concrete slab 10, the wirefabric 12 and antenna feed 14. The antenna array of these figures issubstantially unidirectional. An instrument silo 18 is located at thebase of the antenna and is provided with an access door 16. A pluralityof antenna feeds 14 are connected to the silo 18 by means of leads 20.The plurality of antenna feeds 14 is used to provide a shaped andsteerable beam for directional communication. This is accomplished bycontrolling the phase relationship among the feeds 14 by using phaseshifting circuits located in the instrument silo 18-or in thecommunications center. The power supply for the instrument silo isprovided by cables 22 from the communications center 30 located somedistance from the antenna structure.

The slot as shown in FIG. used in this design is not the conventionalboxed-in slot but is instead a section of waveguide whose characteristicimpedance is matched to that of free space. The walls of the horn 24 aremade from copperplated welded wire fabric and joined firmly to thecopperplated reinforcing screens in the antenna body, giving electricalcontinuity to the entire structure. The input to the antenna feed 26 isa rugged copperplated steel bar. The input is welded to the walls of thehorn and embedded in an insulating medium 28, which may be comprised of90 percent quartz fibers with percent epoxy binder. Such a material willeliminate formation of conducting carbonized surfaces. Because theantenna slot opening has no change of shape in the last foot, there willbe no change in impedance or pattern of the antenna should the top footof the antenna be eroded away as the result of a nuclear blast.

Structurally, experience has shown that there is no doubt as to theintegrity of concrete housings with massive construction, even withloads caused at 2,000 psi overpressure. Furthermore, overheaddetonations tend to drive the antenna into the ground, where it isstrongest.

While there may be some surface spalling, erosion of the surface anddebris piled on the structure the antenna of this invention willcontinue to operate despite such adverse conditions.

Although the invention has been described with reference to particularembodiments, it will be understood to those skilled in the art that theinvention is capable of a variety of alternative embodiments within thespirit and scope of the appended claims.

I claim:

1. An apparatus for sending and receiving radio waves comprising: a massof reinforced concrete with its exposed surface flush with the earthsurrounding it; a plurality of copperplated reinforcing wires embeddedin said mass of concrete and disposed in a plane parallel to the earthssurface; a slot mounted in said mass, said slot being a wave guidefilled with an insulating medium, the impedance of said wave guidematched to that of free space while connected both to the antenna andsending and receiving means.

2. An antenna according to claim 1 wherein the antenna isunidirectional.

3. An antenna according to claim 1 wherein the slot is a crossed slot.

4. An antenna according to claim 3 wherein the antenna isomni-directional.

5. An antenna according to claim 1 wherein containment means areprovided within the antenna for radio frequency circuitry.

6. An apparatus according to claim 1 wherein said insulating mediumcomprises a mixture of substantially percent quartz fibers with a 10percent epoxy binder.

1. An apparatus for sending and receiving radio waves comprising: a massof reinforced concrete with its exposed surface flush with the earthsurrounding it; a plurality of copperplated reinforcing wires embeddedin said mass of concrete and disposed in a plane parallel to theearth''s surface; a slot mounted in said mass, said slot being a waveguide filled with an insulating medium, the impedance of said wave guidematched to that of free space while connected both to the antenna andsending and receiving means.
 2. An antenna according to claim 1 whereinthe antenna is unidirectional.
 3. An antenna according to claim 1wherein the slot is a crossed slot.
 4. An antenna according to claim 3wherein the antenna is omni-directional.
 5. An antenna according toclaim 1 wherein containment means are provided within the antenna forradio frequency circuitry.
 6. An apparatus according to claim 1 whereinsaid insulating medium comprises a mixture of substantially 90 percentquartz fibers with a 10 percent epoxy binder.